Genetics/Biogenesis (sort of)
QUESTION: I was just thinking about Common Descent and this occurred to me. Assume you could trace every living organism on Earth back to a single living organism. Would it be a bacterium or some other thing?
If one were literally motivated to identify a single "first organism" they might need a time machine to find the one pond, puddle, lake or ocean where that happened, and to recognize that theoretically there may have been multiple abiogeneses throughout history. So my next question is, would identifying those events add anything to the science of biology?
Lastly, how do asexual organisms retain some kind of species identity without the ability to trade genetic material? In other words, if the criterion of fecundity is removed as a definition of species, how do scientists decide that a recently diverged form, like E. Coli with a new food source, is or is not a new species?
ANSWER: hi Ralph,
Currently, the oldest life- the ancestors of modern bacteria is thought to be Stromatolites found in Australia. See this link: http://www.bbc.co.uk/science/earth/earth_timeline/first_life
Identifying events - esp geological and palaentological events surely add to determining the life forms in the earliest days.
Asexual organisms have their own unique genetic makeup that allows them the status of a species. They dont have to have sexual reproduction to be given the species status. Speciation is defined by changed in climate, food and environment. When these factors put stress on a species, the organism will evolve and those that confer survival advantage will be retained until the successful 'individual' in the species has accumulated enough new traits that it no longer identifies with it's origin species. At this point it can be called a new species.
---------- FOLLOW-UP ----------
QUESTION: Can bacteria trade genetic material?
If yes, do gene-trading bacteria populations tend to diverge more slowly / less frequently / to a lesser degree than bacteria that are not constrained in that way?
They do have a type of sexual reproduction called Conjugation. In this process bacteria are capable of transferring pieces of their genes to other bacteria that they come in contact with. During this process, one bacterium connects itself to another through a protein tube structure called a pilus. Genes are transferred from one bacterium to the other through this tube.
Bacterial can also take genetic material frome their environment- usually dead remains of another fellow bacteria. This DNA is then transferred thru the cell and integrated to its own DNA. It is still DNA mixing although with a 'dead guy'.